Thursday, February 13, 2014, 9:14:47 PM, you wrote:
> On Tue, 2014-02-11 at 20:17 -0800, Eric Dumazet wrote:
>> On Tue, 2014-02-11 at 18:07 -0800, Dan Williams wrote:
>>
>> > The overlap granularity is too large. Multiple dma_map_single
>> > mappings are allowed to a given page as long as they don't collide on
>> > the same cache line.
>> >
>>
>> I am not sure why you try number of mappings of a page.
>>
>> Try launching 100 concurrent netperf -t TCP_SENFILE
>>
>> Same page might be mapped more than 100 times, more than 10000 times in
>> some cases.
> Thanks for that test case.
> I updated the fix patch with the following.
> diff --git a/lib/dma-debug.c b/lib/dma-debug.c
> index 42b12740940b..611010df1e9c 100644
> --- a/lib/dma-debug.c
> +++ b/lib/dma-debug.c
> @@ -513,6 +513,13 @@ static int active_cln_insert(struct dma_debug_entry
> *entry)
> unsigned long flags;
> int rc;
>
> + /* If the device is not writing memory then we don't have any
> + * concerns about the cpu consuming stale data. This mitigates
> + * legitimate usages of overlapping mappings.
> + */
+ if (entry->>direction == DMA_TO_DEVICE)
> + return 0;
> +
> spin_lock_irqsave(&radix_lock, flags);
> rc = radix_tree_insert(&dma_active_cacheline, to_cln(entry), entry);
> if (rc == -EEXIST)
> @@ -526,6 +533,10 @@ static void active_cln_remove(struct dma_debug_entry
> *entry)
> {
> unsigned long flags;
>
> + /* ...mirror the insert case */
+ if (entry->>direction == DMA_TO_DEVICE)
> + return;
> +
> spin_lock_irqsave(&radix_lock, flags);
> /* since we are counting overlaps the final put of the
> * cacheline will occur when the overlap count is 0.
> Sander, barring a negative test result from you I'll send the attached
> patch to Andrew.
Hi Dan,
That seems to effectively suppress the warning, thanks and:
Tested-by; Sander Eikelenboom <li...@eikelenboom.it>
--
Sander
> --
> Dan
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
